The worrisome new case occurred in Miami-Dade County. No surprise there — this is Ground Zero for the virus. As of Wednesday, Miami-Dade had 89 reported cases, all travel-related. That gives us the unwanted distinction of being No. 1 in the continental United States. The total for Florida, the leading state, is 327.

If the case under investigation is verified, Miami-Dade’s total would be 90, but the danger of infection for everyone here would be much greater. It would mean that the infected mosquitoes are here; that you can catch the virus just by stepping out of your house and being bitten. One doesn’t have to have traveled abroad.

When that starts to happen, infection rates are expected to shoot up rapidly. State and national health officials have been warning about it for months, and yet members of the Republican-led Congress — especially in the House — chose to play politics with this serious public health issue rather than deal with it responsibly.

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Back in February, President Obama asked Congress for $1.8 billion to fight Zika. The response from lawmakers was infuriatingly slow, even as the public health community became increasingly alarmed.

First, the Centers for Disease Control and Prevention said Zika could be transmitted by having sex. Experts warned that something must be done before the onset of summer. Then the World Health Organization advised women at risk of Zika to delay pregnancy to avoid harming the fetus. In June, the first baby infected with microcephaly — a Zika-related birth defect — was born in Florida. Just before the summer recess, health experts pleaded insistently with senators for money to support research on a vaccine and to aid affected communities.

Bupkis. The Obama administration shifted $510 million earmarked for Ebola to fight Zika, a stopgap measure. But Congress sat on its hands. The Senate eventually whittled the original administration request down to $1.1 billion, while the House allocated only $662 million. But the two chambers could never agree on a figure and, ultimately, approved nothing.

The blame lies with the House. It approved legislation to match the Senate total, but only after engaging in an outrageous form of legislative blackmail by attaching irrelevant, poison-pill provisions that Republicans knew Democrats would never accept. In the end, the House adjourned for the summer — the period of greatest risk for mosquito-borne infections — without passing a clean bill to deal with Zika.

In fact, and as shameful, Congress left a long list of unfinished business before lawmakers went off to campaign for reelection and attend the political conventions: a measure to prevent terrorists from acquiring firearms, scores of judicial confirmations, a broad criminal justice reform bill, basic appropriations bills and much more. And, of course, the Supreme Court nomination the Senate refused to hear.

And yet this is the Congress that Speaker Paul Ryan boasted would be a model of legislative productivity to show that Republicans could be trusted to govern effectively. If this is what he calls success, we would hate to see what Mr. Ryan considers failure.